|Publication number||US6846991 B2|
|Application number||US 10/073,641|
|Publication date||Jan 25, 2005|
|Filing date||Feb 11, 2002|
|Priority date||Jan 13, 1999|
|Also published as||US20020100607|
|Publication number||073641, 10073641, US 6846991 B2, US 6846991B2, US-B2-6846991, US6846991 B2, US6846991B2|
|Inventors||Mark T. Girard, Ryan A. Jurgenson|
|Original Assignee||Applied Kinetics, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (34), Non-Patent Citations (2), Referenced by (6), Classifications (23), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a continuation of application Ser. No. 09/274,367 filed Mar. 23, 1999. Abandoned which claims benefit of 60/115,754 Jan. 13, 1999.
The present invention relates generally to methods for eliminating or reducing potential damage to devices from electrostatic discharge or electrical overstress and to such devices, and particularly to methods for reducing such damage to electronic components such as but not limited to a magnetoresistive head forming part of a hard disk drive.
Damage due to electrostatic discharge (ESD) and/or electrical overstress (EOS) costs industry uncounted and perhaps uncountable dollars daily in damaged and irreparable goods. More specifically, ESD/EOS damage is a particular problem in the electronics industry where the components are, of course, designed to conduct electricity in the first instance and where their continuously shrinking size renders them increasingly susceptible to such damaging effects. Generally, ESD refers to actual discharges while EOS refers to the effects of such discharges or currents induced by such discharges or other electrical or magnetic fields. For present purposes, reference to one should be interpreted to include the other.
ESD, familiarly manifested by the lightning bolts or by the shock received when touching a door knob, after walking across a carpet, can range from a few volts to as much as several thousand volts, resulting in extremely large transient currents. As electronic components shrink in size they become ever more susceptible to damage from smaller and small voltages and current.
ESD can arise in several different ways, most commonly as a result of triboelectric charging or induction. Triboelectric charging causes a charge build up due to the frictional engagement of two objects. That is, static charge builds up as a result of a series of contacts and separations of two objects. Electrons travel from one object to the other during these contacts depending on the relative abilities of the objects to gain or lose electrons, that is, depending upon the position of the two objects in the electrochemical potential series. Consequently, a net charge of opposite sign will build up and remain on both of the objects after their separation. Where the object has good conductivity and is grounded, charge will flow to the ground. If the electric field generated by the separated charges is strong enough, an electrostatic discharge can occur in form of a spark traveling across an air gap from one object towards an object at a lower electrostatic potential, thus providing the familiar blue light generated by the spark. This discharge can occur either as one object is brought next to one of the charged objects or as one object is separated from the other.
Static charges can also build up by induction. That is, if a charged object is brought near an uncharged object, the electric field of the charged object will induce a charge in the object, generating an electric field and potentially a static discharge.
A goal in many industries, then, is to determine methods and apparatus for reducing or eliminating static discharges. One of the electronics industries affected by ESD/EOS damage is that which manufactures and assembles computer hard disk drives. As noted above, present hard disk drives include a disk rotated at high speeds and a read/write head that, in industry parlance, “flies” a microscopic distance above the disk surface. The disk includes a magnetic coating that is selectively magnetizable. As the head flies over the disk, it “writes” information, that is, data, to the hard disk drive by selectively magnetizing small areas of the disk; in turn, the head “reads” the data written to the disk by sensing the previously written selective magnetizations. The read/write head is affixed to the drive by a suspension assembly and electrically connected to the drive electronics by an electrical interconnect. This structure (suspension, electrical interconnect, and read/write head) is commonly referred to in the industry as a Head Gimbal Assembly, or HGA.
More specifically, currently manufactured and sold read/write heads include an inductive write head and a magnetoresistive (MR) read head or element or a “giant” magnetoresistive (GMR) element to read data that is stored on the magnetic media of the disk. The write head writes data to the disk by converting an electric signal into a magnetic field and then applying the magnetic field to the disk to magnetize it. The MR read head reads the data on the disk as it flies above it by sensing the changes in the magnetization of the disk as changes in the voltage or current of a current passing through the MR head. This fluctuating voltage in turn is converted into data. The read/write head, along with a slider, is disposed at the distal end of an electrical interconnect/suspension assembly.
Other types or read heads, such as inductive read heads, are known, but the MR and GMR elements enable the reading of data that is stored more densely than that which was allowed with the use of inductive read element technology. MR and GMR read elements are much more sensitive to current transients resulting from voltage potentials and thermal gradients, however, than the previous read element technologies. It is now becoming increasingly necessary to manage environmental electrostatic charge levels to as low 3.3 volts during HGA manufacturing processes so as not to damage the MR and GMR elements. Failing to do so, or failing to provide an avenue for the safe discharge of the accumulated electrostatic charge can result in damage to the MR and GMR heads.
Damage to an MR or GMR head can be manifested as physical damage or magnetic damage. In the former, melting of the read element in the head can occur because of the heat generated by the transient current of the discharge. Magnetic damage can occur in the form of loss of sensing ability and instability. Furthermore, direct discharge into the head is not necessary to create the damage. Damaging current flows in the head can also reportedly be created through electromagnetic interference as a result of a distant (relatively speaking) discharge.
An exploded view of a typical electrical interconnect/suspension assembly is shown in
Stated otherwise, suspension A is essentially a stainless steel support structure that is secured to an armature in the disk drive. The read/write head is attached to the tip of the suspension A with adhesive or some other means. The aforementioned electrical interconnect is terminated to bond pads on the read/write head and forms an electrical path between the drive electronics and the read and write elements in the read/write head. The electrical interconnect is typically comprised of individual electrical conductors supported by an insulating layer of polyimide and typically covered by a cover layer. Prior to the time that the HGA is installed into a disk drive, the electrical interconnect is electrically connected to the read and write elements, but is not connected to the drive electronics. As a result, the individual conductors that make up the electrical interconnect, can easily be charged by stray voltages, thereby creating a voltage potential across the sensitive MR or GMR read elements, which when discharged results in damaging current transients through the read element.
The components shown in
As noted, an ESD can actually damage or destroy circuit pathways in small electronic parts, such as an MR head, requiring the head to be discarded. The industry has been so concerned about this costly manufacturing problem that numerous patents have issued addressing the problem, including but not limited to U.S. Pat. No. 5,867,888 for Magnetic Head/Silicon Chip Integration Method; U.S. Pat. No. 5,855,301 for Electrostatic Grounding System for a Manually Operated Fluid Dispenser; U.S. Pat. No. 5,843,537 for Insulator Cure Process for Giant Magnetoresistive Heads; U.S. Pat. No. 5,837,064 for Electrostatic Discharge Protection of Static Sensitive Devices Cleaned with Carbon Dioxide Spray; U.S. Pat. No. 5,812,357 for Electrostatic Discharge Protection Device; U.S. Pat. No. 5,812,349 for Magnetic Head Apparatus Including Separation Features; U.S. Pat. No. 5,761,009 for Having Parastic [sic] Shield for Electrostatic Discharge Protection; U.S. Pat. No. 5,759,428 for Method of Laser Cutting a Metal Line on an Mr Head; U.S. Pat. No. 5,757,591 for Magnetoresistive Read/Inductive Write Magnetic Head Assembly; Fabricated with Silicon on Hard Insulator for Improved Durability and Electrostatic Discharge Protection and Method for Manufacturing Same; U.S. Pat. No. 5,757,590 for Fusible-Link Removable Shorting of Magnetoresistive Heads for Electrostatic Discharge Protection; U.S. Pat. No. 5,748,412 for Method and Apparatus for Protecting Magnetoresistive Sensor Element from Electrostatic Discharge; U.S. Pat. No. 5,742,452 for Low Mass Magnetic Recording Head and Suspension; U.S. Pat. No. 5,732,464 for Method of Facilitating Installation or Use of an Electromechanical Information-Storage Device Drive Assembly; U.S. Pat. No. 5,710,682 for Electrostatic Discharge Protection System for Mr Heads; U.S. Pat. No. 5,699,212 for Method of Electrostatic Discharge Protection of Magnetic Heads in a Magnetic Storage System; U.S. Pat. No. 5,686,697 for Electrical Circuit Suspension System; U.S. Pat. No. 5,654,850 for Carbon Overcoat with Electrically Conductive Adhesive Layer for Magnetic Head Sliders; U.S. Pat. No. 5,650,896 for Low Cost Plastic Overmolded Rotary Voice Coil Actuator; U.S. Pat. No. 5,644,454 for Electrostatic Discharge Protection System for Mr Heads; U.S. Pat. No. 5,638,237 for Fusible-Link Removable Shorting of Magnetoresistive Heads for Electrostatic Discharge Protection; U.S. Pat. No. 5,589,777 for Circuit and Method for Testing a Disk Drive Head Assembly Without Probing; U.S. Pat. No. 5,491,605 for Shorted Magnetoresistive Head Elements for Electrical Overstress and Electrostatic Discharge Protection; and U.S. Pat. No. 5,465,186 for Shorted Magnetoresistive Head Leads for Electrical Overstress and Electrostatic Discharge Protection During Manufacture of a Magnetic Storage System.
The foregoing patents generally evidence four different methods for reducing or eliminating ESD damage to MR heads, each relying upon the minimization of the voltage potential across the read elements or dissipation of the static electric charge—that is, the creation of an electrical short—and not the prevention of its buildup in the first instance. These methods include the use of mechanical clips, solder bridges, conductive tape, or a tear-away or sheared etched electrical shunt that is manufactured into the HGA by vapor deposition and etching or some other process. While each of these methods has met with some success, each has its own particular disadvantages. For example, mechanical clips are relatively expensive and also require a substantial amount of manual labor to attach them to the electrical interconnect; solder bridges are difficult to attach and then remove without causing damage to sensitive parts, can be a source of contamination in the drive, and also require manual labor for solder application and removal; conductive tape is expensive and requires manual labor for application; and tear away shunts require expensive apparatus, prohibit the electrical interconnect manufacturer from performing badly needed in-process continuity checks on the electrical interconnect, and is intentionally designed as a one-time shunt.
There are disadvantages that are shared by all of the above methods. First, each method is essentially a one-time application of an electrical short. That is, each of these methods relies upon a one-time placement and subsequent removal of the electrical short. Preferred manufacturing and quality testing operations, however, may require the successive application and removal of electrical shorts. For example, prior to in-process read/write head characterization, the electrical interconnect must be de-shunted, and then re-shunted after the head characterization to prevent ESD damage later in the manufacturing process. Yet, as noted, most of the foregoing methods of providing shunts are limited in their ability to be reapplied. This inability to repeatedly create and remove electrical shorts as desired is a critical limitation in present manufacturing operations. In addition, the very act of placing and, particularly, removing the electrical short can cause the very ESD sought to be avoided and, therefore, the damage that the short was to prevent in the first instance.
Further, each of the foregoing methods relies upon a physical engagement with the critical components of the MR head with at least one and sometimes two or more physical contacts, at least with the shunt itself and also, depending upon the shunting method used, with the tool applying the electrical shunt itself to the head. Each of these engagements and disengagements carries with it the potential for damaging the head.
Broadly stated, it would be desirable to have a method of creating and removing electrical shorts as desired in sensitive electronic components that did not depend upon a physical application of a conductive circuit to the component. More specifically, it would be desirable to have a method of creating and removing an electrical short to prevent ESD/EOS damage in an MR head when desired and any number of times desired.
It is an object of the present invention to provide new and improved apparatus that is not subject to the foregoing disadvantages.
It is another object of the present invention to provide a method of repeatedly providing and removing electrical shunts to reduce or prevent ESD/EOS damage.
It is still another object of the present invention to provide a method of using radiant energy to create and remove electrical shunts to reduce or prevent ESD/EOS damage.
It is yet another object of the present invention to provide a method of using a laser beam of a first fluence to create a shunt on the interconnect of the HGA and of using a laser beam of a second fluence to ablate the shunt.
It is another object of the present invention to provide a method of applying a laser beam to the interconnect of the HGA to create a conductive pathway for the dissipation of static electrical charges.
It is still yet another object of the present invention to carbonize a polymeric component of the electrical interconnect of an MR head to create a shunt and to ablate the carbonized surface layer to remove the shunt.
The foregoing objects of the present invention are provided by a method for the substantially at-will creation of conductive pathways for the dissipation of static electric charges and the subsequent at-will removal of such pathways. The method includes the steps of providing an interconnect that is electrically connected to at least one component subject to damage from ESD/EOS; providing a conductive pathway on the interconnect; removing the conductive pathway when the ESD/EOS protection is no longer desired or required; and, if desired, re-establishing and reremoving a new conductive pathway on the interconnect. In one embodiment of the present invention, the conductive pathway is provided by exposing the interconnect's polymeric substrate to a radiant energy source. In another embodiment of the present invention the conductive pathway is removed by exposing the conductive pathway of the interconnect's polymeric substrate to a radiant energy source, which may be the same energy source as used to establish the conductive pathway in the first instance but operated according to different parameters such that the fluence of the radiant energy source is changed between the establishment and the removal of the conductive pathways. The fluence may be changed by increasing the operating power of the energy source or by focusing and defocusing the radiant energy source to alternately concentrate and disperse the energy as desired. In one embodiment of the present invention a laser beam may be used to create the conductive pathway.
The present invention further provides a method whereby a radiant energy source may be used either to carbonize a surface layer of a substrate supporting at least one electrical component or to carbonize the polymericmaterial that engages at least one surface of a pair of conductors. The carbonized surface layer of the substrate or of the cover layer provides an electrical pathway for the controlled dissipation of static electric charges rather than a damaging discharge (either high current transients, or a spark). When it is desired to remove the shunt, a radiant energy source can be used to ablate the carbonized surface, thereby removing the conductive pathway. Lasers can be used both to carbonize the polymeric surfaces of an interconnect to create the conductive pathway and to ablate the pathway when desired.
The present invention also provides for interconnects in accord with the present invention. Such interconnects include at least two conductive wires or leads engaged on at least one surface by a carbonizable and ablatable material. The conductive wires may each include a branched dead end lead portion interleaved with the branched dead end lead portion of the other. Alternatively, the conductive wires may extend in close proximity to each other in a curved or sinuous or serpentine or backtracking pattern. An interconnect in accord with the present invention may include a substrate substantially supporting the conductive wires except at predetermined locations or proposed shunt sites wherein there is at least one through hole in the substrate or the cover layer of the substrate or both.
The foregoing objects of the invention will become apparent to those skilled in the art when the following detailed description of the invention is read in conjunction with the accompanying drawings and claims. Throughout the drawings, like numerals refer to similar or identical parts.
Each actuator arm 20-24 includes a head gimbal assembly 30 comprising a suspension 32, a read/write head/slider 34, and interconnect 36 that extends from the head/slider to the actuator flex 38. The dashed circle shows an expanded view of the arm 20, which includes a substrate 40 (wherein the bracket indicates the lateral extent of the substrate relative to the actuator arm 20 in this particular embodiment) upon which electrical leads or traces 42 are supported. The electrical conductors 42 are typically copper or copper alloy with a gold plating.
The substrate 40 will substantially underlie the traces 42. Substrate 40 may comprise a synthetic material such as polyimide, which may be of the type sold under the brand name KaptonŽ by I.E. DuPont. Polyimide, as is well known, is an organic polymer.
Referring now to
The carbonized layer produced on a polyimide substrate can exhibit resistivities as low as 0.05 ohm-cm, depending upon the carbon density of the created layer. The carbon density of the created conductive surface layer increases with increased pulses of radiant energy and increased fluences, as long as such fluences remain below the ablation threshold.
The present invention, then, provides a method for readily creating and removing a shunt that is completely devoid of any physical contact of the type that either can generate static electrical buildups in the first instance or can cause a discharge in a non-controlled manner. The conductive layer 64 is created by a non-contact application of a radiant energy, such as ultraviolet electromagnetic radiation, which may be created using known laser technology, and can be erased, cleaned, obliterated, or otherwise removed from the substrate as desired. This method enables the assembler of a hard disk drive or other electronic component to create and remove an ESD protecting shunt as desired at least once and typically a plurality of times. In this manner, then, the shunts can be applied, removed, reapplied and re-removed as desired, thereby maintaining a protective shunt in place at all times except when such a shunt would interfere with normal assembly or test procedures, such as when a dynamic electrical test of the read/write head is conducted.
The shunting and de-shunting procedures can be repeated at the same site along the electrical interconnect, or, if desired, at a different site. For shunting purposes, the size of the irradiated site should be considered in determining how to provide adequate conductivity between conductors. A larger irradiated site length will provide lower resistance and better shunting performance.
Suitable radiant energy sources include excimer lasers or solid-state lasers; it being understood, however, that any other radiant energy source capable of preferentially carbonizing the surface of a polymeric material may find employment with the present invention.
More generally, the present invention can be used wherever it is desired to create a shunt between at least two spatially separated, that is, otherwise electrically insulated, electrically conductive components at least partially engaging a common carbonizable insulator, including but not limited to a polymeric substrate or base or cover layer. A source of radiant energy can be used to apply radiant energy to the common substrate or base to create a carbonized surface layer interconnecting the electrically conductive components that will function as an electrical conductive pathway between them. The surface conductive path can be removed as desired using a higher fluence radiant energy source.
Additionally, the present invention can be used wherever it is desired to create a shunt between at least two spatially separated, that is, otherwise electrically insulated, electrically conductive components having at least one surface engaged by a common polymeric overlay. A source of radiant energy can be used to apply radiant energy to the polymeric overlay to create a carbonized surface layer interconnecting the electrically conductive components that will function as an electrical conductive pathway between them. The surface conductive path can be removed as desired using a higher fluence radiant energy source. It will be understood that the present invention will also provide for the carbonization of any other polymeric materials that are disposed between adjacent conductors.
Referring specifically to
Referring now to
It is well understood that certain laser beams do not produce a uniform fluence across the beam area. Therefore, with certain laser beams it may be necessary to include a homogenizer to provide a uniform beam.
It has been found that a carbonized surface can be produced on a polyimide substrate where the fluence level of the applied laser beam is about 60 millijoules per square centimeter (mJ/cm2) and that the carbonized surface can be ablated or otherwise removed at a fluence level of about 140 mj/cm2. Thus, in
Referring now to
As seen in
Referring now to
Another embodiment 160 of an interconnect in accord with the present invention is illustrated in FIG. 11. The interconnect 160 includes a substrate 162 that supports a plurality of leads 164. It will be observed that the interconnect 160 includes a terminal end 166 defining a tear-away or shearable portion 168 and an electrical connect portion 170. Terminal end 166 includes a plurality of temporary, tear away or shearable shunt electrical pads 172 and a corresponding plurality of permanent electrical connection pads 174 electrically connected by a similar corresponding plurality of tear-away or shearable leads 176. Like the connection pads 174, the shunt electrical pads 172 are supported upon a substrate that produces a conductive surface area when exposed to a radiant energy source. Thus the surface areas 178 between the shunt pads 172 can be made electrically conductive. The terminal end 166 also includes a through hole 180 underlying the tear-away leads 176. Thus, with this embodiment, the areas 178 can be shunted and deshunted in the manner hereinbefore described. When the shunt is no longer required, the tear-away portion 168 can be severed from the portion 170, for example, along the dotted line 188. In this manner, then, the entire tear-away portion can be removed from the finished product and no trace of the shunting/deshunting operation will remain.
With the foregoing invention, the thin, carbon surface layer produced on the interconnect has a high resistivity. It is desirable, however, to minimize the resistance between adjacent conductors, such that the majority of a current transient resulting from an ESD event passes through the shunt, rather than the ESD sensitive device. One manner of affecting the resistance is to vary the length being shunted and thus vary the resistance. Thus, increasing the length of the area (length of conductors exposed to the shunt) that forms the shunt will decrease the shunt's resistance.
This following equation describes the relation between the shunt resistance and other variables of interest:
With regards to MR heads, it is generally desirable to provide less total resistance in the shunt than in the read/write head (since current will follow the least resistance path). This can be accomplished by meandering the traces back and forth on themselves in a sinuous or serpentine manner since the increased length of the traces that are shunted results in a decrease in total shunt resistance. Therefore, the affected length of the traces due to the creation of the shunt by the radiant energy source can be longer than with normal non-serpentine traces. For example, normally the length of the traces shunted may be in the range of about 2 to about 4 mm while the length of the shunted traces may be substantially longer, say 30 mm, where a serpentine trace path is used. From the equation above, this results in a reduction in the shunt's resistance of one order of magnitude or a factor of 10.
Simply adding length to the traces is insufficient, however, since negative effects due to the length addition must be avoided. For example, if the length were to be increased in the zone between the actuator flex termination pads and the head, it would increase the trace length between the head and preamplifier, thus diminishing the read and write speed of the head. Positioning of the increased length due to the serpentine or sinuous patter is thus critical to achieving the desired increase in trace resistance without compromising the performance of the read/write head. For example, the serpentine pattern can be disposed past the actuator termination zone and even past the test pads. In that manner, this extra lead (trace) length won't affect drive read or write performance, nor will it impact performance during in-process electrical tests, such as dynamic electrical tests (DET).
The placement of the shunt across the serpentine read leads and the write leads effectively creates a plurality of resistors in parallel, thus lowering the overall resistance of the shunt relative to the leads. Thus, the present invention also provides a method for creating a plurality of parallel resistors useful as shunts to prevent damage due to EDS/EOS.
Referring now to
In each of the
As used herein, “serpentine” is not intended to be limited in its scope to a strictly “back and forth” trace pattern as shown in
The interconnect 300 further includes a cover layer 310, which may be substantially coextensive with the substrate or may be discontinuous. As illustrated the cover layer 310 not only engages the top surfaces 312 of the traces 304A-304D but substantially fills the space between them also. Thus, an interconnect in accord with the present invention may include a plurality of spaced apart traces wherein at least a pair of the traces will each have a carbonizable material engaged or touching at least one surface of the traces. The interconnect 300 includes a plurality of traces encapsulated by carbonizable material, though, as noted, the present invention would include interconnects where only a single surface of the traces contacted the carbonizable material as shown in
Reference will now be made to
After the top surfaces 312 of the leads are exposed, a radiant energy 316 of a second, reduced fluence can be applied to the cover layer to create a carbonized surface or shunt 318 as previously described between a pair of adjacent leads as illustrated in FIG. 15C. The shunt 318 can be removed as illustrated in
It will be observed in
The present invention having thus been described, other modifications, alterations, or substitutions may now suggest themselves to those skilled in the art, all of which are within the spirit and scope of the present invention. For example, rather than creating the shunt directly on the substrate, a carbonizable and ablatable material, such as an adhesive, may be used to fill the spaces between the leads on the substrate. That is, the adhesive or carbonizable/ablatable filler material could be laid down between the leads and then could be converted into a shunt and subsequently removed in any acceptable non-contact method including the application of a radiant energy source such as a laser beam.
In addition, the present invention could find many instances of application during the process of assembling a hard disk drive. By way of example only and without any intent to limit the scope of the present invention or the attached claims, the process could find use while: shunting the slider body of a read/write head; shunting the suspension; shunting a pre-amplifier; shunting a micro-actuator; creating a shunt at a site behind the test pads; creating a shunt a site between test pads and termination pads; creating a shunt at a site between termination pads and head; creating a shunt at an intermediate circuit between the head and actuator flex; or by creating a shunt on a dual layer interconnect.
In addition, by way of example only and without any intent to limit the scope of the invention or the attached claims, the present invention finds use with a laser operating just below the ablation threshold during carbonization; performing the processes at the circuit(component) level process; performing the process at the head gimbal assembly or test process; performing the process at the head stack assembly or test process; performing the process at the drive level assembly or test process; while parts are fed past the laser and optics; while parts are in a holding tray or fixture and the tray is positioned with respect to the laser and optics; while the parts are positioned manually with respect to the laser and optics; while a beam steering mechanism is used to direct the laser beam at the parts being acted on; while measuring resistance during the process for process feedback; while the parts are in an inert environment; while the parts are in an oxygen rich environment; acting on designs that open at the beam perimeter; acting on polymer fill; acting through the substrate; where the polymer is acrylic based; where the material is a composite; using the process in combination with a removable section; using the process on multiple sites along the interconnect to create a plurality of shunts simultaneously or at separate times; performing the process with vacuum or air to remove debris; and while targeting specific resistance values to be achieved in the shunt.
In addition, again by way of illustration and not as a limitation on the invention or the attached claims and as described in some cases above, the present invention may find use on a coverlayer boundary; coverlayer holes; substrate holes; trace separation or routing; with an excimer laser; with an imaging lens; with a mask; with an attenuator; with a laser beam homogenizer; by using the 3rd and 4th harmonic of a Nd:YAG laser; with a polymer/conductor; with a polymer and a semi-conductor; material.
As illustrated herein, the present invention finds a wide variety of applications. It is therefore intended that the present invention be limited only by the scope of the attached claims below.
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|US7006331 *||Sep 30, 2003||Feb 28, 2006||Western Digital Technologies, Inc.||Head gimbal assembly including a trace suspension assembly backing layer with a conductive layer formed upon a gimbal having a lower oxidation rate|
|US7054085 *||Jun 30, 2003||May 30, 2006||Hitachi Global Storage Technologies Netherlands B.V.||Use of shunt resistor with large RA product tunnel barriers|
|US7132607 *||Jun 4, 2004||Nov 7, 2006||Nitto Denko Corporation||Wired circuit board|
|US7389577||Jun 26, 2007||Jun 24, 2008||Western Digital (Fremont), Llc||Method to fabricate an ESD resistant tunneling magnetoresistive read transducer|
|US20040245015 *||Jun 4, 2004||Dec 9, 2004||Takeshi Yoshimi||Wired circuit board|
|US20040264067 *||Jun 30, 2003||Dec 30, 2004||Hitachi Global Storage Technologies||Use of shunt resistor with large RA product tunnel barriers|
|U.S. Classification||174/250, 174/261, G9B/5.038, G9B/5.037, G9B/5.039|
|International Classification||H05K1/00, G11B5/115, G11B5/11, H05K1/16, H05K1/02|
|Cooperative Classification||H05K2203/1136, H05K1/0259, H05K2203/107, H05K1/167, G11B5/112, G11B5/11, G11B5/115, H05K1/0393, H05K2201/0323|
|European Classification||H05K1/02C6C1, G11B5/11, G11B5/11A, G11B5/115|
|May 24, 2005||CC||Certificate of correction|
|Aug 4, 2008||REMI||Maintenance fee reminder mailed|
|Jan 25, 2009||LAPS||Lapse for failure to pay maintenance fees|
|Mar 17, 2009||FP||Expired due to failure to pay maintenance fee|
Effective date: 20090125